"As a Senedd community we are all devastated by the tragic news of Hefin’s death.
"Our thoughts go immediately to his partner, our colleague and friend, Vikki Howells MS and to his cherished children and family."
The Welsh Parliament is the democratically elected body that represents the interests of Wales and its people.
Commonly known as the Senedd, it makes laws for Wales, agrees Welsh taxes and holds the Welsh Government to account.